Process for the catalytic conversion of hydrocarbons



Jan. 2, 1951 LA VERN' H. BECKBERGER 2,536,254

PROCESS FOR THE CATALYTIC CONVERSION OF HYDROCARBONS Filed June 1'7, 1947 F G. H FRESH GATALYS FLUE GAS TO PRECIPITATOR 0R STACK VAPORIZED' CHARGE on.

LOUVERS REACTION ZONE GENERATING ZONE AIR RECONVERSION PRODUCTS STEAM AND HYDROGARBONS AIR INVENTOR I LAVERN HERBERT BEOKBERGER LOUVER Patented Jan. 2, 1951 UNITED STATES PROCESS FOR THE CATALYTIC OONVER- SIGN OF HYDROCARBONS La Vern Herbert Beckbergcr, East Chicago, Ind., assignor to Sinclair Refining Company, New

York, N. Y., a corporationof Maine Application tune-17, 1947, Serial No. 755,199

1 f This invention relates to the pyrolytic conversion of hydrocarbons and, more particularly,

to pyrolytic conversion processes involving the use of a solid catalyst.

In such operations, a carbonaceous deposit is formed on the solid catalyst during the hydrocarbon conversion and the catalyst must be periodically regenerated to restore its catalytic effectiveness.

In one method of operation previously proposed, the hydrocarbons to be converted are passed continuously upwardly through a downwardly gravitating bed of catalyst in granular or pelleted form in a vertically elongated con-. version chamber of large transverse dimensions, the catalyst being continuously withdrawn from the lower end of the chamber, regenerated, and returned to the upper end of the chamber. The

regeneration is efiected by burning off the carbonaceous deposit by passing the hot catalyst downwardly through a similarvertically elongated chamber countercurrentto a stream of air.

.Such operations have entailed expensive and troublesome mechanical elevator'means for conveying the catalyst from the lower end. ofthe conversion chamber to the top of the regenerating chamber and again from the lower endof the regenerating chamber to the top of the conversion chamber. Difficulties have also been experienced in .eifecting uniform contact between the hydrocarbon vapors and the catalyst by.

reason of the tendency of the vapors to channel upwardlythrough. the bed of catalyst. Similar difiiculties have been experienced in the regeneration of the catalyst. The present invention provides an improved method of operation whereby these diiiiculties are avoided.

In accordance with my present process; the catalyst at an elevated temperature iscaused to gravitate as a continuous, vertically elongated bed or column downwardly through a vertically elongated chamber of comparatively small transverse dimensions.

.The hydrocarbon vapors to be converted are repeatedly passed back and forth through the downwardly gravitating vertically elongated bed of hot catalyst at progressively different elevations whereby conversion of the hydrocarbons is effected with resultant. deposition. of carbonaceous material on the catalyst. The. spent catalystis passed from. the lower end ofthe reaction zone into. the lower end .of a. second vertically.

ro aim. (on. 196 52) upper and lower portions of the reaction zone.-

elongated chamber, advantageously. of equal .or.- greaterheight than .the reaction chamber and,-

with advantage, in heat exchangerelation with a the reaction zone.

wardly through the second chamber by suitable 2 The catalyst is passed up means, for instance, a helical screw conveyor, and controlled quantities of air are introduced intothe second chamber at a plurality of vertically spaced positions, whereby the carbonaceous deposit is progressively burned oil from the catalyst.

The amount of air passed to the lower portion of the regenerating zone in contact with the catalyst higher in carbonaceous material is, with advantage, so restricted as to retard combustion toan extent sufficient to avoid excessive temperature rise. At progressively higher zones, ad-

.ditional fresh air is brought into contact with the partially regenerated catalyst in amounts.

sufficient to burn off residual carbonaceous ma.- terial.

.As. previously noted, the regenerating zone is, with advantagein heat exchange relationship.

with the reaction zone and a portion of the regeneration heat is transmitted to the reaction zone. This is particularly desirable in operations involving endothermic reactions and efiectively.

reduces thetemperature gradient between the Where the regenerating zone is not in heat exchange relationship with the a reaction zone,

conventional means for cooling the walls of the.

regenerating zone may be provided. The tem-, 'perature of the catalyst passing from the regenerating zone to the reaction zone may further be controlled by the introduction of cool air into the upper portion of. the regenerating chamber.

Heat for effecting the conversion is supplied in large measure, at least, by the burning of the carbonaceous deposit. Additional heat may be supplied where required by preheating the hydrocarbon vapors or the regenerating air, or both.

Hydrocarbon vapors to be converted may be passed through the catalyst bed at progressively higher, or. progressively lower levels, that is, in a generally countercurrent or generally concurrent direction with respect to the direction ot the catalyst flow.

Due. precautions should be taken to minimize intermixing of hydrocarbon vapors and the.

gaseous products of theregeneration. Further,. it is desirable to strip the spent catalyst of. vaporizable hydrocarbons 'prior to passing the. spent catalyst to the regenerating zone.

This is, with advantage, accomplished by passing a gaseous stripping medium through the catalyst in the lower portion. ofthe vertically elongated regenerating chamber.

In a particularly advantageous method of operation, in accordance with my invention, the hydrocarbon vapors are repeatedly passed through the column of catalyst, at progressively lower levels in the reaction chamber, and steam or other gaseous inert stripping medium is passed through the catalyst in the lower zone of the reaction chamber at progressively higher levels. The stripping medium and stripped hydrocarbons may be withdrawn from a zone lower than that from which the conversion products are withdrawn. or they may be intermixed and withdrawn from a common zone.

Catalyst fines are frequently formed by attrition of the catalyst during repeated circulation through the system and it is usually necessary to remove these fines to avoidtheir excessive accum lation. In accordance with my present invention, the catalyst fines are carried on from the system in suspension in the gaseous products of combustion from the "regenerating zone.

"By proper control of the rate of downward flow of the catalyst bed and coordinating therewith the rateof flow and number of passes of the hydrocarbon va ors therethrough. the catalyst will be substant ally spent and ready for regeneration by the time it reaches the lower end of the reaction zone. Further. by'proper control of the rate at whi h the catalyst is carried u wardlv through the re n rating zone and the amount of air passed thereto. the catalyst will be complet ly regen rated and ready for reuse inthe conversion o eration by the time it reaches the pper end of the re enerat n zone.

The o timum rate of downward flow of the catalvst bed will depend rimarily upon the t pe of catalyst em lo ed. the t pe of hydrocarbon bein convert d. operat ng tem rat res. the rate of hvdrocarbon feed. the extent of the required rea t on. the de th of crack ng, for instance, the num er of a ses tb'rm'i h the ata t an the thickness of the catalyst bed. The optimum rate of catal st f ow for any part cular operation is rea'd lv determ nable b sim le test and is on trolled by the rate o'f'the passa e of theca'talvst from the react on zone to'the' renegeratin zone wh h. in turn. is c nt1'oll 'd'bvthe rate of the upward passa e of tli'e"catalyst' th ou h'tne re generat ng'zone, by the rate" of operation of the cvn evor. I- l :The' process is a pl cable'to vario s t pes of hvdrh arhnn con er i n and cont m lates the' use of vario s solid catal st in ranu ar or nellete rm. 'l'li 'nr s wil h more narti ula lv de crib d and il t ated w th reference to the acc m an ing drawing. of whi h:

Fi re 1 re r sents a v rti al section of a particular-1v a antageou t e of a aratus. t of mv conend applicat on. Ser. No 755 2' 0. fil ncurr nt-1v her withfiand now Patent No. z s nass. i sued March 14 1950.

Fi re 2 is a cr s sectional view'of the apparatus alon the lin s 2---: and

'Fi n'r 2 i a ross s t onal ew of a modified form of a a atus having a cylindr cal sect on;

"The anparatu 'isho s ed in a asim I. advantaeemislv o sheet metal and. enclosed at ts p er an lo r n s. re p ctive y; b cover p te 2 and a bottom plat The' asin'r' may be either re tan ular. a h n in Figure 2, or cylindrical, as hown in Figure 3.

Ref rr n more pa ticularl to the modificat on repr sente b the F Q l R-Q 1 and 2. the inter or of' the a paratus is divided into three sect ons by partitions 4 and 5, vertically positioned Within {and at its lower end by bearing :5 and adapted to be driven by any convenient source of power,

not shown in the drawing, through pulley I6.

Attached to the lower side of the flights of the helix and spaced apart are downwardly extending. fins ll. The lower end of these fins are spaced a substantial distance above the upper surface of the next lower flight, but are of suflicient depth to prevent the spiraling of gaseous medium upwardly along the lower surfaces of the flights without substantial contact with the catalyst.

Each of the sections 6 and I is completely obstructed by a plurality of vertically spaced partitions l8 dividing the sections into a plurality of vertically spaced chambers, each of which communicates with zones 8 through louvers, the slats of which project upwardly and outwardly into the respective chambers.

The partitions l8 are, with advantage, positioned somewhat as shown in the drawing so as to form separate chambers in the zones 6 and l in staggered positions such that the lower end of a given chamber is directly opposite the upper end of the next lower chamber in the opposite end section. These partitions [8 are. for clarity, shown in the drawing as solid sections, but it will be understood that they may be either solid or hollow. Further. for reduction in weight and material used in fabrication, the casing I may be discontinuous at the points of the respective partitions l8.

The cylindrical casing I 0 terminates short of theupper end of section 8 and likewise terminates at its lower end short or the bottom of section 8. It is supported by suitable brackets, or the like, not shown in the drawing.

In charging for operation, the zone 8 is filled with granular catalyst, for instance, introduced through conduit l9 and during operation fresh catalyst is introduced from time to time as required through conduit 19. or continuously at a rate controlled by valve 20. Vaporized hydro-' carbon oil to be processed is charged through line 2| into the uppermost chamber of section I and, from thence, by way of the louvers flows through the body of catalyst in section 8 and into the uppermost chamber of section 6. From the lower'portion of said chamber of section 6. the vapors pa s back-from the body of catalyst into v The catalyst which has been substantially spent continues downwardly through section B and is stripped of readily vaporizable hydrocarbons remaining thereon by steam, or other gaseous stripping medium introduced into the lowermost chamber of section 6 through line 23.

From thence, the steam passes by way of the '7 louvers" through the catalyst bed in the lo'wer-- were inost portion ofsection"-8---into the lowermost chamber of section I and, from thence, back through the body of catalyst into the next higher chamber of section from which the stripping medium and strippedhydrocarbons are withdrawn through line 24.

.The. stripped catalystis picked. up from the bottom of'section 8'by the helicalscrew conveyor and is"c arried upwardly therebylthrough chambeirIS from the upper endof which the catalyst passes by gravity onto the upper end of the body dfeatalyst'insection 8. In operation, -section .8 is kept substantially filled with catalyst.

Air is introduced in controlled amounts, as previously described, into chamber 9 at vertically spaced positions through lines 25. Contact of the air with the hot catalyst results in the combustion of the carbonaceous deposit on the catalyst and the products of combustion pass upwardly through the chamber 9 into the upper end of the section 8 from which they pass through conduit 26 to a precipitator, or stack, not shown. spiraling of the air upwardly along the lower side of the flights is, as previously noted, prevented by the downwardly projecting fins [1.

The horizontal path of the hydrocarbon vapors, and of the stdipping medium, through zone 8, from zone I to zone 6, is lengthened and uniformity of contact thereof with the catalyst is increased, with advantage, by means of baffles 21 and 28 shown in Figure 2 of the drawings.

In Figure 3 'of the drawings, the casing l is cylindrical and the zones 5 and I are formed by a second coaxially positioned cylindrical casing 29 and partitions 30, extending vertically between casings l and 29. In this arrangement, uniformity of contact between the hydrocarbon vapors and the catalyst is promoted and the length of the path of the vapors through the catalyst is increased by means of vertically extending baffles 3| and 32.

The apparatus is shown in Figure 1 of the drawing as partly broken away to indicate greater depth of the spacers 18. Usually these partitions or spacers should be of a depth at least equal to, or somewhat greater than, the length of the path of the vapors through the catalyst bed, so as to minimize any tendency of the gases or vapors to pass directly from one chamber to a chamber immediately above, or below rather than through the catalyst bed to the opposite chamber. Some by-passing of the vapors from one zone to the next higher or lower zone frequently does not seriously interfere with the operation. However, in order to obtain the full benefit of my present process such by-passing of the vapors should be minimized and this may usually be accomplished by increasing the depth of the spacers.

The apparatus shown in the drawing provides for four passes of the hydrocarbon vapors and for two passes of the stripping medium through the catalyst bed. Frequently a greater number of passes of the hydrocarbon vapors is desirable and is within the contemplation of my invention.

The amount of air and the rate at which it is injected into the regenerating zone at the various elevations will depend primarily upon the amount of carbonaceous material deposited on the catalyst and will vary with other operating conditions. The rate of flow of the hydrocarbon vapors through the catalyst is also subject to considerable variation and will depend upon the number of passes, the type of catalyst, the type inert carriers having active catalyst deposited thereon. The size. 01 the... particlesof catalyst is, with advantage, of a .mesh within the range of Zo-to 4o, though catalysts of larger and smaller particle size may.be.employed;. Pelleted catalyst as coarse as l. to 10 mesh 'may be employed. Usually powdered catalyst, such as usedl in'tli'e. filllq. catalyst process, is less desirable because of a tendency of the catalyst particles to be carried out or the catalyst bed along with the vapors and stripping medium, but may be used in con junction with relatively low vapor velocities through the catalyst bed.

Operating conditions are generally subject to considerable variation, depending upon the particular catalyst employed and the nature and extent OI the desired reaction. In ci'acxing gas oil, for instance, using a silica-alumina type catalyst, the temperature in the reaction zone is, with advantage, maintained within the range or about 1 750 to 950 F. and the pressure within the range V of about 10 to lo pounds per square men. In the regenerating zone, a temperature within the range of sun to ll50 F. is usually satisractory.

The temperature in the reaction zone is dependent in large measure at least upon the temperature or the catalyst passing to the reaction zone from the regenerating zone and may be controlled, as previously described herein. Where the regenerating zone is in heat exchange relationsliip with the reaction zone, the temperature in the reaction zone will also be influenced by the temperature in the regenerating zone.

By the present process, the extent of contact between the catalyst and the hydrocarbon vapors being converted, and also the catalytic activity of the catalyst with which the hydrocarbon vapors are brought into contact, may be maintamed extremely unir'orm. Also, the temperature gradient in the reaction zone may be substantially reduced. Further, an exceptionally uniform and complete regeneration of the catalyst is attained. The process has the advantage or high unlr'ormlty or the product, increased catalyst lite and catalytic erlectiveness, increased economy or operation and also closer control of operating conditions.

I claim:

In a process for the pyrolytic conversion of hydrocarbons carried out in a single vessel wherein hydrocarbons in vapor phase are continuously passed in intimate contact with a solid catalyst at an elevated temperature, resulting in the formation of a carbonaceous deposit on the catalyst, and in which the catalyst is regenerated by burning off the carbonaceous deposit by contact with air, the improvement which comprises passing the catalyst in a relatively narrow, vertically elongated body downwardly through an enclosed vertically elongated chamber, efiecting conversion of the hydrocarbons by repeatedly passing the hydrocarbon vapors transversely through the body of hot catalyst at progressively lower elevations, removing the converted hydrocarbon vapors from the chamber at a lower point, stripping the occluded hydrocarbons from the catalyst by passing steam into the bottom portion of the chamber, passing the spent stripped catalyst from the lower end of said vertically elongated chamber to the lower end of a second vertically elonmam 7 gated chamber in heat exchange relationship with the first said chamber, mechanically con- 'Jeying the catalyst upwardly along a spiral path through the second said chamber, regenerating the catalyst'during its upward passage by introducing-air concurrently into the ascending catalyst at a plurality of vertically spaced zones-in controlled'amount and passing the regenerated catalyst by gravity from the'upper end of the second chamberonto the upper end of the vertically elongated body'of catalyst in the first chamber."

" LA VERN HERBERT BECKBERGER.

8 REFERENCES CITED I ffhe following references are of record in f le of this patent:

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' Putney Apr.'15,' 

